The Section remains focused on preparing a first-in-human clinical trial of AAV gene therapy for the central nervous system (CNS) problems in Alpha-mannosidosis (AMD), a prototypical lysosomal storage disease (LSD) for which no suitable therapy for the CNS effects currently exist. Our novel research strategy of targeting the choroid plexuses (CP) to treat the brain disease has narrowed the AAV therapeutic candidates to two specific serotypes based on testing four total in the mouse model of this illness. The optimal serotype and dose, once finalized, will undergo preclinical toxicological evaluation in concert with FDA guidance and be proposed as the IND for the human clinical trial. AAV vectors injected into the CSF target the CP, highly vascularized structures that project into the brain ventricles. The polarized CP epithelia (CPE) produce CSF, regulate the biochemical milieu of the brain, and secrete numerous proteins. We hypothesized that many LSDs could benefit from a CP-targeted approach by secreting vector-encoded normal lysosomal enzyme (LE) into the CSF, which extends throughout the ventricular system to the subarachnoid space, Virchow-Robin spaces, and interstitial fluid space from which molecules ultimately reach the entire brain. Secreted normal lysosomal enzymes (LE) would be taken up and utilized metabolically by diseased neural cells. AAV-mediated gene therapy would provide a long-term (if not permanent) source of normal LE since AAV vector payloads are mantained as episomal transgenes in cells, and CPE cells are know to have an extremely slow rate of turnover. The aims of this project are to complete pre-clinical studies, conduct additional studies requested by the FDA after a pre-preIND conference, obtain an IND, and begin a phase I clinical trial. The potential impact in the field of LSDs is high since, if the proposed aims are achieved, the largest current barriers to health for patients with AMD and other LSDs affecting the brain would be circumvented.